Over 90 million Americans have basic or below basic literacy skills, which are independently associated with poor understanding of health information, poor health behaviors and poor clinical outcomes. Prior work from our study team has demonstrated that lower health literacy or numeracy is associated with lower rates of breastfeeding, problems mixing infant formula, difficulty understanding food labels and portion sizes, difficulty understanding growth charts, higher Body Mass Index (BMI) in adults and children, and difficulties with medication dosing and other safety issues. However, to date, there has been limited study of the evolving role of parent literacy in the long-term health of young children, and most studies have only been cross-sectional. In 2009, we were awarded a 5-year NIH R01 to perform a cluster randomized trial to evaluate the impact of a health literacy/health communication intervention on early childhood obesity prevention (known as the Greenlight Intervention Study) in four academic primary care clinics. Two clinics received a health literacy sensitive intervention for obesity prevention, while two active control sites received education in injury prevention. English- and Spanish-speaking parents and their infants were enrolled at the child's routine 2 month-old preventive care visit and are followed until the child is 2 years old. Throughout the study, multiple measures of child health status are collected, including clinical indicators (e.g., child weight and length, immunization status, health-care utilization), behaviora indicators (e.g., dietary and physical activity, injury prevention behaviors), and health communication-related assessments (e.g., parent health literacy/numeracy, perceived provider communication). Recruitment of 865 families was completed September 1, 2012. Retention rates have been promising to date, with >90 percent of eligible families completing their 2 year visits. Cross-sectional analyses of data from the baseline 2 month well-child visit demonstrated significant associations between low literacy and increased obesogenic behaviors and worse injury prevention behaviors. Preliminary results at 4 and 6 months suggest that the intervention improved dietary and physical activity-related infant care behaviors. Through this competing renewal, we propose to continue to follow this unique child cohort, which we call the Greenlight Cohort Study, with data collection through phone surveys and in-person interviews every six months until children are 5 years old. This will allow us to assess the long-term effects of the original intervention. In addition, this longitudinal cohort will provide us the opportunity to examine the relationship between parent literacy and early childhood health-related outcomes, including family health behaviors, child obesity, injury, and child development. This study will also contribute new information on the validity of parent literacy measures over time in the context of child health. The proposed study will provide the most robust understanding to date of the role and importance of parent health literacy in early childhood obesity prevention and other child health-related issues and shape future interventions to curb obesity and improve child health.